Subject: [Bridge-mib] Question of link aggregation groups in Q-Bridge portList

From: "chungwei wu" <[email-masked]>
Date: Mon, 10 Dec 2001 10:24:24 -0800

Hi All

I am currently working on the Q-Bridge MIB and Link Aggregation Group task, 
and have a question about the portList port mapping in the Q-Bridge MIB. I 
hope you guys could share some of your valuable thoughts on this.

Question: Should Q-Bridge portList accommodate both physical port and Link 
Aggregation Group?

When Q-Bridge was finished in 1998, IEEE 802.3AD was not
completed yet. The portList in Q-Bridge only defines how the port should be 
mapped to each bit in the portList, but it does not define the port number 
assignment schema - how port number is assigned to each port in the switch. 
The standard leaves this to the vendors.

I think the port in Q-Bridge should cover both physical port and logical 
link aggregation groups. If a switch supports upto 96 physical ports and 32 
LAGs, the lenght of portList would be 128 bits.

It is interesting that RiverStone RS16000 switch supports Q-Bridge MIB but 
Cisco Catalyst switches/Extreme black diamond/Foundry BigIron switches do 
not claim Q-Bridge MIB support and use their own proprietary MIB for VLAN 
membership management.

Any comments are welcome.

Best regards,
Chungwei Wu

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From: Michael MacFaden <[email-masked]>
Date: Mon, 10 Dec 2001 14:56:52 -0800

>Question: Should Q-Bridge portList accommodate both physical port and Link 

I believe it already does. A dot1dBasePortNumber from rfc1493 which
is represented with the aggregate object "portList" in 2674 may be abstract or
physical. It may or may not be related to an ifIndex which also
may or may not be physical.

>LAGs, the lenght of portList would be 128 bits.

Indeed. And it gets interesting when one actually takes two ports
that are currently assigned a dot1dBasePortNum then are removed
from the bridge and added to the LAG, thus creating a new dot1dBasePortNum.

So the bit length of a PortList can be dynamic..
note: dot1dBasePortTable can be sparse too.

Here is our implementation's documentation:
http://www.nmops.org/download/rs-snmp-mgmt.pdf page 63.

It is an interesting with what to include in the 
dot1dBasePortTable. A device that supports many 
different technologies besides bridging may also lead to diffferences
in what shows up across vendors or a given vendor's products
in the dot1dBasePortTable. If seen that some devices include 
all ports that can possibly bridge, others include ports that bridging packets, 
while others include ports that are bridging packets and running 
a control protocol such as stp...

Regards,
Mike MacFaden